Laser scanning confocal microscopy is a state-of-the-art technology for-high resolution fluorescence and reflectance microscopy. This year, a laser scanning confocal microscopy system was acquired by the Cell Components Laboratory. Unlike conventional epifluorescence microscopy, which frequently has out-of-focus flare of the fluorescence image, confocal microscopy enhances the contrast and resolution of images by rejecting out-of-focus information. The microscopy system provides the opportunity to obtain a series of thin optical sections through a specimen, store each of the sections on a computer, and reconstruct the image series as a stereo image or 3-dimensional image. Several studies are in progress in our laboratory using this new technology and they are outlined below. 1. Cytoskeletal changes in chemoattractant-stimulated neutrophils. Specific fluorescent probes for filamentous actin are used to map the location of actin filaments during the activation of neutrophils with chemoattractants. Time course studies of the actin filament location and quantitative image analysis of the fluorescence signals are performed to determine the pattern of actin filament assembly and morphologic change during neutrophil stimulation. Oscillations in this response have been observed with flow cytometric measurements of the total filamentous actin. Studies are in progress to determine the location of the actin filaments during the oscillations in filament assembly 2. Quantitation of the peri-nucleolar region of normal and neoplastic cells. Specimens stained with silver stain for the nucleolar-organizing region of normal and neoplastic cells are analyzed using reflectance confocal microscopy. These studies are performed in collaboration with Dr. Robert Becker, AFIP, Washington, D. C.